The invention relates to a continuous process for making steel from ore, pellets, sinter, etc. in a shaft furnace.
Reduction processes are known under the general term "direct reduction processes" whereby ore or pellets are converted to iron and sponge iron. These processes are carried out in various types of apparatus. Best known is the direct reduction process of coarse ores or pellets in a shaft furnace or of fine ore and coal (for instance coke) in a rotary furnace. The final product is sponge iron which usually has a residual contents of unreducible oxygen and in addition contains, in the form of contaminations gangue components of the ore which are not amenable to reduction.
This intermediate product is therefore then usually subjected to a second independent operation where it forms, so to speak, the starting product for scrap iron in the conventional steel production apparatus. Unfavorable in this stage however is the high porosity, that is large surface, which causes a tendency to reoxidation. Extended unprotected storage and melting methods under oxidizing conditions therefore have an undesirable effect.
For the latter reason it is customary to melt down sponge iron formed in a direct reduction process in electro-furnaces. In these electro-furnaces the sponge iron is preferably fed into the furnace in a continuous charge as distinguished from the conventional discontinuous bucket charge.
It is therefore an object of the invention to provide for a process wherein sponge iron which has been produced as customary in a shaft furnace can be melted down in the same apparatus in a continuous operation and can be discharged as steel.